High impact information on RPB3

• Sequence alignments, combined with secondary-structure predictions, support proposals that a heterodimer of the eukaryotic RNAP subunits related to Saccharomyces cerevisiae Rpb3 and Rpb11 plays the role of the alphaNTD dimer in prokaryotic RNAP [1].
• Although multiple functions have been assigned to the three largest subunits, RPB1, RPB2, and RPB3, the functions of the remaining smaller subunits are unknown [2].
• These data indicate that RPB2 and RPB3 form a complex that subsequently interacts with RPB1 during the assembly of RNA polymerase II [3].
• Finally, the RPB3 protein is similar in sequence and length to RPC5, a subunit common to RNA polymerases I and III, suggesting that these subunits may play similar roles in RNA polymerases I, II, and III [4].
• RPB3 was found to be an essential single-copy gene that is tightly linked to HIS6 on chromosome IX [4].

Biological context of RPB3

• To improve our understanding of RNA polymerase II, the gene that encodes its third-largest subunit, RPB3, was isolated from a lambda gt11 DNA library by using antibody probes [4].
• The RPB3 DNA sequence predicts a 318-amino-acid protein whose sequence was confirmed, in part, by microsequence analysis of the gel-purified RNA polymerase II subunit [4].
• RNA polymerase II subunit composition, stoichiometry, and phosphorylation were investigated in Saccharomyces cerevisiae by attaching an epitope coding sequence to a well-characterized RNA polymerase II subunit gene (RPB3) and by immunoprecipitating the product of this gene with its associated polypeptides [5].
• RPB3 is encoded by a single copy gene in the yeast, mouse and human genomes [6].
• In the case of Rpb3, growth was restored by increasing the gene dosage of the host Rpb11 or Rpb10 subunits, confirming previous evidence of a close genetic interaction between these three subunits [7].

Anatomical context of RPB3

• Due to the failure of skeletal muscle cells to differentiate when exposed to dox, we hypothesized that RPB3 is involved in muscle differentiation [8].

Associations of RPB3 with chemical compounds

• Glycerol gradient fractionation of extracts of cells pulse-labeled for various times revealed that a subcomplex of RPB2 and RPB3 appears soon after subunit synthesis and can be chased into fully assembled enzyme [3].
• Determination of the precise orientation of the RNAPII in the holoenzyme indicates that Mediator contacts are centered on the RNAPII Rpb3/Rpb11 heterodimer, the eukaryotic homolog of the alpha(2) homodimer involved in transcription regulation in prokaryotes [9].

Other interactions of RPB3

• We have sequenced two different cDNAs (AtRPB36a and AtRPB36b), the two corresponding genes from Arabidopsis thaliana that are homologs of yeast RPB3, and an Arabidopsis cDNA (AtRPB13.6) that is a homolog of yeast RPB11 [10].
• Under certain circumstances, RPB3, RPB4, and RPB7 were cross-linked [11].
• The existence of Rpb5-Rpb3 contact was supported by detection of complexes formed between these two proteins synthesized in vitro using protein-immobilized beads [12].

References